Shudder at initial acceleration

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Nicholle, May 6, 2026 at 3:22 PM.

  1. Nicholle

    Nicholle New Member

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    Hi all!

    I have looked through here and haven't quite found a post that is like my issue so I'm hoping someone has some insight. My prius has developed this shudder when I press on the gas pedal. It was worse when I first started the vehicle after it had sat for about 3 hours. The gas engine had kicked on and I put the car in reverse, when I pressed the gas there was a strong shudder. I waited a second or so and tried reversing again, no shudder. When I came to my first stop and the engine cut off, the car shook again pretty aggressively. After this, it seemed to only have a less intense shudder when I first hit the gas pedal. The best way I can describe the feeling is similar to a torque converter failing on a gas vehicle, but it occurs when I first accelerate vs. at ~ 45mph.

    I of course ran to google and all I can find is spark plug and/or ignition coils potentially being the issue. I have spark plugs on the way already and were going to change them this weekend, but wondering if it could potentially be something else more serious. Thanks!
     
    #1 Nicholle, May 6, 2026 at 3:22 PM
  2. JC91006

    JC91006 Senior Member

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    You can run a live test and see if there is a cylinder that's misfiring. Techstream or similar software can do that. The spark plugs are rated for about 120k miles so if yours are older than that, then you should change them. But I feel your problem would be bad fuel injectors. If the spark plugs or coils would be an issue, it would not improve as the car warms up.
     
    #2 JC91006, May 7, 2026 at 10:22 AM
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  3. saneesh8

    saneesh8 Member

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    How many miles? Also the engine mounts are in good shape ? You can try cleaning the fuel injectors.
     
    #3 saneesh8, May 7, 2026 at 10:58 AM
  4. Tombukt2

    Tombukt2 Senior Member

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    When this is occurring the engine is bucking or making that torque converter noise. Do you see chk engine light or trac light flicker ??
     
    #4 Tombukt2, May 7, 2026 at 11:37 AM
  5. Nicholle

    Nicholle New Member

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    Thanks! Fuel injectors was my next guess but I wanted to try the spark plugs first since they are on the way. The car has 179K miles and fairly new to me so I am not sure they were ever changed. There's no info on the carfax about it, so I'm just assuming not.
     
    #5 Nicholle, May 7, 2026 at 11:37 AM
  6. Tombukt2

    Tombukt2 Senior Member

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    Sounds to me like you're going to have misfire codes pretty easy to check orieleys etc . The head gasket issue and all that nonsense is pretty rare on a generation 2 until we'll abused
     
    #6 Tombukt2, May 7, 2026 at 11:38 AM
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  7. Nicholle

    Nicholle New Member

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    There is no noise from what I can hear. No dash lights and I ran my OBD2 scanner and no codes!

    Sorry I should've included miles - 179K! Engine mounts looked good to me, but I'm no expert lol. I can have someone a little more knowledgeable check on that for me though.
     
    #7 Nicholle, May 7, 2026 at 11:38 AM
    Last edited by a moderator: May 7, 2026 at 7:34 PM
  8. Tombukt2

    Tombukt2 Senior Member

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    The next thing to do is take your four spark plugs out . Take a poly tube about 15 inches long maybe 5/16. Stick hose in spark hole watch it go in the plug hole not just the well. Now sniff the tube gently . Smell.coolant? Check the other three cylinders if you have an inkling of coolant odor . That's yer issue . . Or you rent a inspection cam
     
    #8 Tombukt2, May 7, 2026 at 8:19 PM
  9. Nicholle

    Nicholle New Member

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    Will do! Thank you!
     
    #9 Nicholle, May 7, 2026 at 8:46 PM
  10. pasadena_commut

    pasadena_commut Senior Member

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    Where are the spark plugs from? Amazon is full of counterfeits. Plugs from a dealer or RockAuto should be the real deal. This applies to all OEM parts.

    This matters because often the counterfeit will make the car run worse than the old OEM part which it replaced.
     
    #10 pasadena_commut, May 8, 2026 at 8:49 PM
  11. Tombukt2

    Tombukt2 Senior Member

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    The bad plugs come apart in engine . Soon as bad running starts get home whip em out and look well with a loupe .take plug in hand by the top and shake like you drawing down a thermometer for you're kid before digital. Hear the rattle yep .
     
    #11 Tombukt2, May 9, 2026 at 7:51 AM
  12. Nicholle

    Nicholle New Member

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    I ordered them off Amazon per someone’s recommendation but I just placed an order for pick up at oreilly’s after reading your comment! Thanks!!

    Thanks so much for all your help!! I’ll be replacing them today so I’m hoping that is my issue. But I know for next time to check asap. I really appreciate your help.
     
    #12 Nicholle, May 9, 2026 at 9:33 AM
    Last edited by a moderator: May 9, 2026 at 1:48 PM
  13. Nicholle

    Nicholle New Member

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    Update: I changed the spark plugs and the shudder is gone! I’m still planning to take it to a mechanic just to look over everything, but I’m hopeful this was the cause and is fixed. Thank you everyone for the help!!
     
    #13 Nicholle, May 9, 2026 at 4:16 PM
  14. Tombukt2

    Tombukt2 Senior Member

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    Yes the plugs are probably fixed and starting to come apart hopefully. You caught it and everything you took out looks like a spark plug nothing's missing
     
    #14 Tombukt2, May 9, 2026 at 4:42 PM
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